The present disclosure relates to a solid-state imaging device, driving method and electronic device. In particular, the present disclosure relates to a solid-state imaging device, driving method and electronic device that can suppress power consumption in a device such as an image sensor without degrading image quality.
In recent years, on the ground of high-speed performance of the reading speed, replacement of CCDs with CMOS image sensors has been advanced. However, in the CMOS image sensors, the reading is generally performed every pixel in order, and therefore it is not possible to realize synchronism in the whole image.
That is, the CMOS image sensors perform an operation of sequentially scanning and reading light charges generated and accumulated in a photoelectric conversion portion every pixel or every row. In the case of this sequential scanning, that is, in the case of adopting a rolling shutter as an electronic shutter, it is not possible to share the exposure start time and exposure end time to accumulate light charges, in all pixels. Therefore, in the case of the sequential scanning, there is a problem that distortion is caused in a taken image at the time of taking an image of a moving subject.
In the case of taking an image of a subject that moves at high speed in which that kind of image distortion is not allowed, or in the case of the sensing use requesting synchronism in a taken image, a global shutter to execute the exposure start and the exposure end at the same timings with respect to all pixels in a pixel array portion is adopted as an electronic shutter.
A global shutter device, which is a device adopting the global shutter as an electronic shutter, includes, for example, a charge accumulation portion by a semiconductor memory in pixels. In the global shutter device, charges are concurrently transferred from a photodiode to a semiconductor memory, accumulated and sequentially read, so that synchronism in the whole image is maintained.
Also, there is suggested a device mounting a capacitor in addition to a semiconductor memory that accumulates charges to expand a dynamic range of an image sensor. In such a device, since it is possible to accumulate a large amount of charges by accumulating the charges in the capacitor, it is possible to improve the dynamic range and simultaneously realize image synchronism and the dynamic range improvement (for example, see Japanese Patent Laid-Open No. 2011-199816).
For example, in the case of Japanese Patent Laid-Open No. 2011-199816, two accumulation portions are provided. One is formed with a flush-mounted channel in a Si substrate and the other is formed with a capacitor.
The flush-mounted channel is formed under an SG part and has a feature that, since the possible accumulation capacity is small and the accumulation is performed in Si, it is less influenced by the interface state and the dark current is small. Meanwhile, the capacitor can accumulate a large amount of charges compared to the flush-mounted channel.